In the manufacture of a semiconductor device, a process of filling a semiconductor material such as silicon or the like into a depression such as a hole or a trench formed on a surface of a semiconductor wafer may be performed. The semiconductor wafer includes a semiconductor substrate and an insulating film formed on the semiconductor substrate. The depression is formed in the surface of the insulating film (the surface of the semiconductor wafer). The semiconductor material filled into the depression is the same as the material of the semiconductor substrate and is often used as, e.g., an electrode.
In the related art, there is known a method and apparatus for filling a depression formed in an insulating film of a workpiece which is a semiconductor wafer. The depression filling method includes a step of forming a first amorphous silicon film containing an impurity along a wall surface which defines a depression, a step of forming a second amorphous silicon film on the first amorphous silicon film, and a step of annealing the workpiece after the second amorphous silicon film is formed.
A depression provided on a surface of a semiconductor wafer may be formed so as to pass through the insulating film and extend up to an inside portion of a semiconductor substrate which serves as a base of the insulating film. This depression is formed by etching the insulating film and the semiconductor substrate. The present inventors have been studying a technique in which a depression is filled by moving a semiconductor material toward the bottom portion of the depression and forming an epitaxial region conforming to crystals of a semiconductor substrate from the semiconductor material. In this study, the present inventors have found that in a method of filling a depression by virtue of solid-phase epitaxial growth, when a region in which epitaxial growth is not performed is included in the inner wall surface of the depression, epitaxial growth is not performed in that region. As a result, the filling by an epitaxial region is not sufficiently performed in the depression and cavities may be partially formed in the depression. Accordingly, in the technique of filling the depression by virtue of the epitaxial growth of the semiconductor material, there is a need to suppress the formation of cavities within the depression.